docs: add SERVICE_DOCS.md for all 24 microservices from per-service code audit
Each SERVICE_DOCS.md documents: Overview, API Endpoints, Commands, Queries,
Domain Model, Database Schema, Integration Events, Dependencies, Configuration.
Generated by 23 parallel audit agents reading actual source code.
Key corrections from audit:
- inventory-service: 12 commands/6 queries (was listed as scaffold)
- promotion-service: 12 commands/10 queries (was listed as 0)
- mission-service: 4 commands/7 queries (was listed as 0)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>